Columbium-base alloys



United States Patent 3,346,380 COLUMBIUM-BASE ALLOYS Lutfi H. Amra, Cleveland, Ohio, assignor to General Electric Company, a corporation of New York No Drawing. Filed Jan. 4, 1965, Ser. No. 423,358 8 Claims. (Cl. 75174) ABSTRACT OF THE DISCLOSURE Columbium-base alloys containing by weight 4-15% tungsten and 0.55% rhenium have been found to be ductile at room temperature in a welded condition and in a recrystallized condition and have useful strengths in the temperature range of 2000-2500 F. Optional additions include 05% hafnium, O3% molybdenum, 0-5% tantalum, O3% zirconium, 00.1% carbon, 00.5% yttrium, 0-0.1% boron, and 0-0.l% of oxygen, nitrogen and mixtures thereof.

The present invention concerns novel columbium-base alloys having ueful strengths at elevated temperatures in combination with good ductility and fabn'cability at low temperatures. More particularly, the invention concerns such alloys hardened by solid solution means, and in some cases also hardened by precipitation mechanisms.

In the continuing efforts toward making available alloys having useful properties at ever higher temperatures, it has been a constant aim to discover and develop alloys which have desirable combinations of properties at elevated temperatures and at room temperature, both in terms of physical, mechanical and chemical properties needed to meet certain application goals, and in terms of workability and general ruggedness in the environment which the alloy must be able to withstand.

Accordingly, it is an object of the present invention to provide novel columbium base alloys which have useful strengths in the temperature range of 2000-2500 F. and higher, in combination with workability at lower temperatures and ductility at room temperature.

Another object of the invention is to provide such tentional additions with the analyzed content not being controlled to be anything other than zero. For control of grain size on casting, prevention of grain growth, and for other purposes, alloys of the invention may also include up to 0.5% yttrium and up to 0.01% boron. Additions of hafnium and zirconium generally serve to render alloys of the invention hardenable by precipitation mechanisms in combination with carbon and perhaps also with other interstitial elements such as oxygen and nitrogen in addition to the solid solution hardening enhanced by tungsten, rhenium, molybdenum and tantalum. Specified preferred alloys within the invention include one containing about 9% tungsten, 1.6% rhenium, 1.8% hafnium and 0.05% carbon, the balance essentially columbium; another containing about 15% tungsten, 2% rhenium, 3% hagnium and up to 0.1% carbon, the balance essentially columbium; and another containing about 4.4% tungsten and 3.3% rhenium, the balance essentially columbium. The hafnium-bearing alloys may also include the specified amounts of oxygen and nitrogen.

Examples Five different alloys within the invention were produced, farbricated and mechanically tested to determine their utility. The nominal and analyzed compositions of these alloys are presented in Table I below, with the balance in each case being columbium. The nominal composition is that of the additives that were melted together with columbium to form an ingot. The analyzed compositions diifer from the nominal composition since the additives volatilize at difie-rent rates from the liquid pool during the melting operation. In the format of Table I, both the nominal and the analyzed amounts of each constituent, such as tungsten, are given for each alloy such as alloy No. 1. The nominal amount precedes a diagonal line and the analyzed amount follows the diagonal line. Thus, the differences between nominal and analyzed composition and the relative volatilities of the constituents are readily apparent from the table. A dash before the diagonal means that none of the constituent was added to the alloy, and the letters na after the diagonal indicate that the element was not analyzed. P.p.m. means parts per million.

TABLE I.ALLOY COMPOSITIONS (NOMINAL/ANALYZED) Alloy Percent P.p.rn.

W Re Hf Other 0 o H N 4. 7/4.4 4. 8/3. 32 -/na -/na /na -/na 8/6. 5 2/1. 65 2 1. 53 1, 000/130 /90 /e0 8/7. 78 2 1. s 1 0. a 2/2. 2 Mo 1, 000/ /90 /2 /53 5. 4.7/4.79 4.8/3.02 2/na 1,000/00 /na /na /na 6. 10/9 1. 6/1. 0 2/1. 8 600/450 /70 /3 /60 alloys which are capable of retaining ductility in a welded Alloys 1, 2, 3 and 5 were double melted by electron condition and in a recrystallized conditlon. 60 beam techniques to ingots 1.5 inches in diameter and Briefly stated, the present invention in one form provide-s a columbium-base alloy consisting essentially of 4-15% tungsten, 0.55% rhenium, the balance being essentially .all columbium. (Percentages herein are by weight except where indicated otherwise.) Other embodiments may include up to 5% hafnium and up to 0.1% carbon. In still other embodiments, the alloys of the invention may also include, in addition, up to 3% molybdenum, up to 5% tantalum, up to 3% zirconium and up to 0.1% of elements from the group consisting of oxygen and nitrogen and mixtures thereof. The term up to herein is meant to include essentially zero, i.e., no in- 3 inches long. Alloy 6 was melted once by are casting to an ingot 2 inches in diameter and 3 inches long.

After melting, the ingots were machined to sound metal, canned in molybdenum,'and extruded to rectangular shapes having cross-sections of about 1.145 x 0.830 inches at about 1200 C. The extrusion ratio was approximately 4:1. Hardness measurements were made on the front ends of the extrusions at room temperature as indicated in Table II below. The measurements were made by the Diamond-Pyramid-Hardness method (DPH) using a 10, kilogram load. The values in Table II are the averages of 5 readings.

TABLE II.HARDNES'SAS EXTRUDED Alloy No.: Hardness-DPH 218 .184 196 After extrusion, each alloy was rolled at about 800 C., using a 20% reduction in thickness per pass for a total of 50% reduction. Rolling was then continued at 600 C. for another 50% total reduction, after which the molybdenum jacket was removed. Finish rolling to 0.075 inch thick sheet was done at room temperature. The finished sheet was then conditioned by surface grinding to remove about 0.008 inch from each side and cleaned in acid to remove any contamination that might be present.

Tensile specimens 0.060 inch thick, having a gauge length of 0.50 inchand a gauge width of 0.250 inch were machined from the resulting sheet, and the specimens were annealed as stated in Table III. As noted in the table, one specimen was more rapidly cooled than the others by the addition of helium to the furnace after annealing.

Table III also shows the results of tensile testing at various temperatures of the alloys of the invention. UTS' =(p.s.i.) means ultimate tensile strength in poundslperJ square inch;*0.2% Yield is the 0.2% yield strength in Y pounds per square inch; Elong. is the percent elongation over a 0.50 inch gauge length. Testing was done at a strain rate of 0.04 inch/ inch per minute =until 0.6% offset yield, and then 0.1 inch/inch per minute until fracture in an evacuated chamber at a'pressure of less than 10 mm. Hg.

TABLE III.TENSILE TESTING 4 What I claim as new and desire to secure by Letters Patent of the United States is:

. 1. A columbian-base alloy consisting essentially of, 'by weight, about: 4 15 tungsten, 0.55% rhenium, 5% hafnium, 0 3% molybdenum, 0-'5% tantalum, 0-3% zirconium, 0-0. 1% carbon, 0-0.5% yttrium, 0-0.01% boron,

and 00.l% of elements selected from the group consist ing of oxygen and nitrogen and mixtures thereof, the balance being essentially all columbium.

1 2. A columbium-base alloy consisting essentially of, by

weight, about: 415% tungsten, 0.55% rhenium, 0-5% hafnium, 03% molybdenum, 05% tantalum, 0-3% zir-.

conium, -00.5% yttrium, and 00.-0'1% boron, the balance being essentially all columbium. V

'3. A columbium-base alloy consisting.essentiallyof, by weight, about: 4 tungsten, 0.55% rhenium, 05% hafnium, 03% molybdenum, 0 5% tantalum, and 03% zirconium, the balance being essentially all columbium.

4. A eolumbium-base alloy consisting essentially of, by weight, about: 4-15 tungsten and 0.55% rhenium,. the balance being essentially all columbium.

5. A col-umbium-base alloy consisting essentially of, by weight, about: 41'5% tungsten, 0.55% rhenium, 1-5% hafnium, 0-0. 1% carbon, and 00.'l% of elements selected from the group consisting of oxygen and nitrogen and mixtures thereof, the balance being essentially all. columbium.

6. A columbium-base alloy consisting essentially of, by weight, about: 9% tungsten, 1.6% rhenium, 1.8% hafnifromthe group consisting of oxygen and nitrogen and Alloy Test UTS 2% Elong. Annealing Condition F.)

No. T egp). (p.s.i.) Yield (percent) 73,700 50, 900 r 38 2,550, 36 hr. 1 2, 200 15, 500 9, 200 58 2,400, 1 hr.

3, 000 7, 700 5, 200 2,550, 92 hr. 3, 000 8,380 5, 730 74 2,400, l hr. 2 3, 000 7, 250 4, 730 70 5 2, 200 17, 800 9, 600 56 2,550, 9*; hr. 3, 000 8, 000 5, 66 2,200, 56 hr. 2,700 15, 610 9, 520 62 2,550, l hr' 6 3,000 9, 560 6,800 104 2,550, V hr.

3, 000 8, 800 6, 900 46 Agedt at 3,300, 1 hr. He cooled, es e Annealed sections from alloys Nos. '2 and 6 were due 'tile in a standard bend test, exhibiting about a 2T bend radius at room temperature after electron-beam welding.

(T is equal to the thickness of the sheet being bent.) Under the proper conditions, various alloys of the invention should also be'ductile after welding bytungsten-inert-gas techniques Alloy No. 6, having an approximate composition of ed the highest strength in combination with ductility after welding of the alloys of the above examples, in addition to being readily fabricable. It is anticipated that other alloys within the limits of the invention may be superior to this alloy 6 in at least some properties. Although absolute optimization of alloys of the invention would require the testing and evaluating of an infinite number of permutations and combinations of constituents along with the variables introduced by thermal and mechanical processing, the above examples demonstrate the utility of the novel alloys of the invention. They have useful strengths in the temperature range of 20002500 F. and higher in combination with fabricability and ductile weldability.

While specific examples have been given of alloys of the invention, it will be understood that various changes, omissions and substitutions may be made within the true spirit and scope of the invention as defined in the'appended claims.

mixtures thereof, the balance being essentially all colum- 011mm. V a V 7. A columbium-base alloy consisting essentially of, by weight, about: 15% tungsten, 2% rhen ium, 3%'hafnium and up to 0. 1% carbon, and 040. 1% of elements selected from the group consisting of oxygen and nitrogen and mix- 55 tures thereof, the balance essentially all columbium;

, 8. A columbium-base alloy consisting essentially of, by weight, about: 4.4% tungsten and 3.3% rhenium,.the balance essentially all columbium.

OTHER REFERENCES 7 WADC Technical Report 57-344, Development of Niobium Base Alloys, Begley et al., September 1961, relied on pages 58-62.

7 CHARLES N. LOVELL, Primary Examiner.

um and 0.05% carbon, and 00.1% of elements selected a 

1. A COLUMBIUM-BASE ALLOY CONSISTING ESSENTIALLY OF, BY WEIGHT, ABOUT: 4-15% TUNGSTEN, 0.5-5% RHENIUM, 0-5% HAFNIUM, 0-3% MOLYBDENUM, 0-5% TANTALUM, 0-3% ZIRCONIUM, 0-0.1% CARBON, 0-0.5% YTTRIUM, 0-0.01% BORON, AND 0-0.1% OF ELEMENTS SELECTED FROM THE GROUP CONSISTING OF OXYGEN AND NITROGEN AND MIXTURES THEREOF, THE BALANCE BEING ESSENTIALLY ALL COLUMBIUM. 